Percy dunsheath



Jan. 10, 1933. p, D Re. 18,710

EXTRUSI ON OF METAL PIPES-AND THE LIKE ori inal Filed June 26, 1950 I Jnl/htor. fibym Reisaued Jan. 10, 1933 I UNITED STATES PATENT OFFICE PERCY DUNSHEATH, OF SIDC'UP, ENGLAND, ASSIGNOR '10 W. T. HENLEYS TELEGRAPH WORKS COMPANY LIMITED, OF LONDON, ENGLAND EXTENSION OF METAL PIPES AND THE LIKE Original No. 1,817,301, dated August 4, 1931, Serial No. 463,879, filed June 26, 1930, and. in Great Britain July 1,1929. Application for reissue filed October 11, 1932. Serial No. 637,297.

This invention relates to the extrusion of metal pipes and the like and to the application of lead or like sheaths to electric cables. The usual method of producing pipes or cable sheaths of lead and its alloys is to employ a hydraulic press, including a cylinder or container charged with molten-lead which,

as it cools is forced forward in a semi-molten state through an annular space between a die and apoint by the advancement of a ram. In such an apparatus variousfactors contribute to difiiculty in maintaining uniformity of thickness of the sheathing, whilst the provided for supplying molten lead or lead alloy to said screw thread by which it i extruded, after solidification, in the form of a tube or cable sheath.

According to the present invention either the casing or the point holder or core may be rotatable relatively to the other, and either one of said members may be formed with the i screw thread, and'the other with the longitudinalribs and/or grooves, whilst in order to produce a smooth exterior and interior surface on the mass of metal without the formation of fissures and folds therein, the screw thread on one member and the ribs and /or grooves on the other member (lie away toward the outlet end, the former dying away before the latter.

It is desirable that a small clearance should be left between the two relatively rotatable members, whilst, where required, a suitable shaping die maybe provided at the outlet end of the apparatus.

Where a cable is to be sheathed by the apparatus, the point holder forms a tube .through which the cable is fed so thatas it passes out through a die, it is surrounded by the extruded metal.

Preferably, means are provided for cooling the outer of the two relatively rotatable concentric members beyond that part thereof where the molten metal enters it.

In order to prevent relative rotation be-.

tween the metal and the walls'of the passage stationary, whilst the ribs and/ or grooves do not die away completely until after the have passed the junction between the screw t readed member and its extension.

The continuous movement of the metal in the narrowannular space between the relatively rotatable concentric members makes it an easy matter to obtain accurate temperature measurements of the metal at different points in the, length of the passage, and accurately to control the temperature gradient in the metal, so that the metal which enters in the molten state can be made, by appropriate control of the cooling, to'change from the liquid to the solid state as it travels forward.

One form of apparatus for carrying the invention into effect is shown by the accompanying drawing in which Figure 1 is a sectional elevation; Figure 2 a section of a modified detail and Figure 3 an enlarged crosssectionof the core or point holder.

As illustrated a central hollow point holder a 'is fixed centrally in a vertical position with respect to a vessel '6 which is surrounded by acylindrica'l casing d on which casing said vessel is rotatably mounted in ball bearings e and adapted=to be driven by a shaft f through bevel wheels g g. The casing Z) carries a coaxial driving sleeve it formed at its inner surface with a screw thread i which dies away at the outlet end of said sleeve which is located within a sta tionary member 7' carrying a die is mounted i .with a flange It received in a groove formed I between the stationary member j and the means not shown), whilst a gas burner 0 or y internal flange of an L-section ring 7" which is secured to said member j by means of bolts j, the thrust of said flange h being taken by the ring j through the medium of a ball.

bearing. h

The lower end of the vessel 1) is submerged in molten metal contained in the casing d which is supplied from a tank n (heated by other heating means is provided for maintaining the temperature of the lead in the casing d. i

The arrangements are such that the vessel 6 is adapted to be rotated round the, point holder a, its bearings being arranged at a sleeve.

part remote from the hot part in contact with the lead and ensuring true con'cent-ricity of the die In and the oint m. The outer surface of the point older a is formed with longitudinal grooves p leaving ridges g (see Figure 3) said grooves dying out toward the upper end, beyond the upper end of the driving sleeve h, their function being to prevent the general mass of metal enclosed between the driving sleeve h and the point holder a from being carried round bodily by said The temperature gradient along the apparatus is controlled by cooling devices such as water or oil circulating pipes, approriately disposed, or by airblown thereinto or which latter purpose a coaxial flange 1- in the vessel b is apertured' as at s t and an annular channel u opening opposite the aperturess is supplied with air (which may be cooled) through apipe 'v, the air passing through the a ertures 8 into contact with'the outer wall of t edriving sleeve h and passing away through the apertures t.

T e molten metal flows from the tank n tothe casing d to approximately the level in-- dicated at w and on enterin the lower end of the space between the drivmg sleeve h and the'point holder a is fed upwards by gravity until it has solidified-and thereafter by the action of the internal screw thread 'i as the vessel b'and driving sleeve h are rotated. In

' the lower part of the sleeve 72. the drive exerated by the screw thread i is. loose owing to the fluid state of thelead, but as the latter becomes solid, the drive becomes effective, and

. the thread '4' exerts thepressure necessary to force the metal between the die is and the point m. In the upper part of the sleeve h where '-or partmay be as inFigure 1 son the grooves p die away before the point m is reached, but after the screw thread i has died away, i. e. after the lead stream has reached the stationary part "7'.

The inner surface of the stationary part j may be as indicated in Figure 1,- or in some cases its lower part may be cylindrical until the grooves p have died away to prevent any risk of folding of the lead. 'By suitable selection of the pitch and, the rate of reduction of the size of the thread 2', of the area of cross sectionof the lead stream between the sleeve h and the point holder a and of the temperature gradient, the pressure required for the extrusion of the metal can be obtained;

Instead of forming the sleeve h with screw thread i which dies away at its upper end only, by cutting away the tops of the thread, it may die away by cutting a tapered thread throughout the whole length of the sleeve and then boring its 'cylindrically, as in Figure 2,

and part tapered as in Figure 2.

Itisdesirable that the temperature of the molten metal just-before it enters the space between the sleeve h and point holder (1 should be just above (say 5 to 10 F.) the melting point of the metal so as to ensure solidification of the metal as soon as possible after it has entered said space.

When the apparatus is to be employed for V sheathing electric cables or the like, the point holder a is hollow and fitted over an aperture w in the bottom of the casing d to the under-surface of which is secured a suitable guide such as is shown at y. v

The above description refers to apparatus in which the centrally grooved point holder is fixed ina vertical position and is surrounded by an internally threaded cylindrical rotatable casing, but it is to be understood that this holder may be fixed in a. horizontal pos1- 'tion, and the casing may be mounted so as to rotate on a horizontal axis, whilst means are provided for feeding molten metal into one end of the space between said point holder and said casing.

1. Means for the continuous extrusion of metal pipes and the like, comprising two relatively rotatable concentric members the inner one of which forms a point holder 9r core and the outer one of which forms a casing, one of said membersbeing formed with vided for supplying molten lead or lead alloy to said screw thread by which it is extruded after solidification in the form of a tube or cable sheath, in which the screw thread on one member and the ribs and/or grooves on the other member die away toward the outlet end, the former dying away before the latter, in order to produce a smooth exterior and interior surface on the mass of metal without the formation of fissures and folds in the metal.

"2. Means for the continuous extrusion of metal pipes or the like as claimed in claim 1, in which a central grooved point holder is fixed in a vertical position and is surrounded by an internally threaded cylindrical rotatable casing, mounted so as to rotate on a vertical axis, while the lower portion is submerged in molten metal.

3. Means for the continuous extrusion of metal pipes and the like, comprising two relatively rotatable concentric members, the inner one of which forms a point holder or core and the outer one of which forms a casing, one of said members being formed with a screw thread and the other with longitudinal ribs and/or grooves, means being provided for supplying molten lead or lead alloy to said screw thread by which it is extruded after solidification in the form of a tube or cable sheath, in which the metal passes through three distinct zones in the apparams, the first of which is an impelling zone where there is little or no diminution in the depth of the screw thread or grooves, the

surface on a member which is stationary or rotary according as said last mentioned member is stationary or rotary in order to produce a smooth exterior and interior surface on themass of metal without the formation of fissures and folds in the metal.

4. Means for the continuous extrusion of in fixed position is surrounded by an internally threaded cylindrical rotatable casing,

- mounted so as to rotate concentrically of said point holder, while means are provided for feeding molten metal into one end of the space between said point "holder and said casing.

5. Means for continuous extrusion of metal v pipes and the like, comprising two relatively rotatable concentric members the'inner one of which forms a point holder or core and the outer one of which forms a casing, said outer member being formed with a screw thread and said inner member with longitudinal ribs and/or grooves, means being promember or casing in such manner as to perm1t relative rotation therebetween and so .that the tensile force generated in the apparatus and tending to separate the outer member or casing and the shaping die, as a result of the compressive forces in the metal under extrusion, are resisted in the locality of said die without change in the general direction of the flow of the metal.

6. Means for the continuous extrusion of metal pipes or the like as claimed in claim 5, in which the screw thread on one member and the ribs and/or grooves on the other member die away toward the outlet end in order to produce a smooth exterior and interior surface on the mass of metal before it reaches the extruding die wit-houtthe formation of fissures and folds in the metal.

7. Means for the continuous extrusion of metal pipes or the like as claimed in claim 5, in which a central grooved point holder is fixed in a vertical position and is surrounded b an internally threaded cylindrical rotata ile casing, mounted so as to rotate on a vertical .axis while the lower portion is submerged in molten metal.

8. Means for the continuous extrusion of metal pipes and the like, comprising two relatively rotatable concentric members, the inner one of which forms a point holder orcore and the outer one of which forms a casing, said outer member being formed with a screw thread, and said inner member with longitudinal ribs and/or grooves, means being provided for supplying molten lead or lead alloy to said screw thread by which it is extruded after solidification in the form of a tube or cable sheath, a suitable shaping die being secured to the adjacent end of said outer member or casing in such manner as to permit relative rotation therebetween and so that the tensile force generated in the apparatus and tending to separate the outer member or casing and the shaping die, asa result of the compressive forces in the metal under extrusion, are resisted in the locality of said die without change in the general direction of the flow of the metal, there being three distinctzones in the apparatus, the first of which is an impelling zone where there is little or no diminution in the depth of the screw thread or grooves, the second of which is still within the space between the rela-. tively rotatable concentric members where the screw thread on the outer member dies away, but through which the ribs and/or grooves onthe inner member continue, and

the third of which is a zone bounded, on

the one hand, by the continuation of the inner member on which the ribs and/or grooves die away, and, on the other hand,

' by a smooth surface on a member which is stationary or rotary, according as said inner A member is stationary or rotary.

9. Means for the continuous extrusion of metal pipes or the like as claimed in c1aim8,

inwhich the internal screw thread on the casing, and the ribs and/or grooves on the lower portion is point holder, (lie away towards the outlet end, said point holder being fixed in a ver tical position and said casing being mounted so as to rotate on a vertical axis while the submerged in molten metal.

PERCY DUNSHEATH. 

